Electric forming apparatus



July 27, 1943- w. E. CRAWFORD ELECTRIC'FORMING APPARATUS Filed Dec.

FIG. 4.

William 15. Crawford INVENTOR. fi/ v M ATTORNEY Patented July 27, 1943 STES T ELECTRIC FORMING APPARATUS Application December lll, 1942, Serial No. 468,525

8 Claims.

This invention relates to electric forming apparatus and is applicable to th forming of cylindrical objects into symmetrical shapes such as the fianging or closing of tubes and the reduction in diameter or upsetting of tubes and rods.

The invention more particularly relates to electrio forming machines in which a cylindrical object is pushed into a confining die mad up of segments constituting electrodes for applying heating current to the article in the region of forming, the die and article being relatively rotated during the process.

The principal object of the invention is to provide a more efficient apparatus having a greater path of current flow through the article being heated and which can be readily adjusted for difierent article sizes and shapes.

Another object is to greatly increase the speed "1 forging and consequent production from a single machine.

Either objects and the following desc ct merit of the invention partying drawing.

In the drawing:

Figure l is a side elevation of the machine;

2 is a forward. elevation of the forming dies showing the electrical connections;

Fig. 3 is a longitudinal section through the dies, taken on line of 2; and

Fig. 4 is a transverse section through the dies,

antages will appear in a preferred embodi taken. on line dl of 8.

The machine comprises in general two spaced upright standards i and 2 carrying the operative partsof the machine. Standard i supports the, chuck for gripping the rear end of the tubular blank 3' and rotating and feeding the blank or other article being formed. For thi purpose the chuck 3 is rotatably mounted in a fram 5 which is slidable toward and away from the standard 2 under suitable driving power such as the screws 6 rotated by motor l. A second motor 83 on the frame it is connected to rotate the chuck 3 as the latter is fed forward.

The standard 2 supports the forming dies and transformers. The forming dies preferably comprise six separate segments arranged in a circle and having complementary inner faces for enillustrated in the accorngaging and forming the blank 4. Three segments 9, Hi and H constitute electrodes for applying heating current to the pipe 4 and the remain ing three intermediate segments 52, it and iii are of substantial width for separating the electrode segments to provide a long current path through the article between the latter.

The die segments ii to ill, inclusive, are constructed of copper and preferably have water cooling passages therein and also die inserts it of special alloy material to provide for wear of the die surfaces as set forth in the copending application of John M. Floyd, Serial No. 395,804, filed May 29, 1941, for Dies for electrical forging machines, and assigned to a common assignee herewith.

The die segments are secured together by end rings ii in a manner similar to that set forth in the copending application of the present inventor, Serial No. 396,668, filed June 5, 1941, for Electric heating and forming apparatus.

The transformers it, it and are disposed radially outwardly from the respective die segments til, it and i i. The primer oi? the several transfo; cers are preferably co between the separate leads e source of three-phase alternating cu .ovide a different phase for each transfc;

The secondary of transformer 2:1 and connected to the electro through separate circuhiiercntially em uding ous bars and respectively. The secondary or" the transformer has its leads d 29 con-- n cted to the electrodes m and l ugh the separate circiunferentially extending and 3t, respectively. Likewise, the secondary of the transformer 2t has its leads ii an connected to the electrodes ii and 9 through the bus bars and 26, respectively. In this construction each electrode has a separate bus bar for supplying current to it; electrode 9 having bus bar 26; electrode it having bus bar 2i; and electrode it having bus bar 3%]. are secured to their respective electrodes by bolts 33 and extend in opposite directions circumfer entially from their electrodes so that the seconclary leads of each transformer are parallel and close together.

The transformer connections to the electrodes are at the forward or open end of the die to The bus bars side of each electrode. This provides at least two regions where each-of the heating currents have to pass through the blank. In addition to this, it is preferable to make each of the intermediate die segments in two or more parts separated by insulation 34, for instance. This gives an additional gap where the heating current must flow beneath the insulation and through the blank 5. To further minimize the flow of current through the die faces at the insulated section. these faces may be slightly flattened as described in the application of Sven Westin et a1., Serial No. 458,216, filed September 14, 1942, for Electric forming.

The several insulations 3d are located preferably'midway between the pairs of electrodes and radially in line with the space between the respective pairs of secondaryleads of the transformers. The insulation 3 may be cut out to the rear of the bus bars to provide space for the insertion of laminated magnet core material for I choking current flow longitudinally of the electrodes, as more particularly set forth in application, Serial No. 396,668, above referred to.

The intermediate die sections I2, l3 and It, beneath the bus bars should be constructed of non-magnetic highly-conductive metal such as copper, since this will reduce the amount of flux traversing the loop between the leads by reason of the opposing flux set up by eddy currents.

The segments 9 to It, inclusive, may have the same shape and size and be interchangeable. However, in some instances the electrodes 9, Ill and H may be pointed toward the rear and the intermediate segments may extend back with substantially uniform width, and in other instances the electrodes 9, Ill and Il may have substantially parallel sides and the intermediate segments l2, l3 and it may be pointed toward the rear.

The number of electrodes and transformers may be varied, the lowest number. being one transformer and two electrodes. able in some instances to have the die surface of the electrodes extend radially inward slightly farther than'do thedie surfaces of the intermediate sections to provide for greater contact pressure between the electrodes and-blank.

Various embodiments of the invention may be employed within the scope of the accompanying claims.

The invention is claimed as follows:

1. In an electric formingapparatus, a die providing a die cavity for receiving and forming .an article, said die comprising a plurality of circumferentially spaced segments at least two of which constitute electrodes and are substantially spaced apart with at least one intermediate segment insulated therefrom, and means to supply electric current to said electrodes for heating the article as it enters saiddie. v

2. In an electric forming apparatus, a die It is also desirarranged in a circle to provide a die cavity for receiving and forming an article, said die segments being insulated from one another, and means supplying electric current to a plurality of said segments with intermediate insulated segments therebetween.

3. In an electric forming apparatus, a die comprising a plurality of spaced die segments of non-magnetic electrically-conductive material arranged in a circle to provide a die cavity for receiving and forming an article, said die segments being insulated from one another, and means supplying electric current to a plurality of said segments with intermediate insulated segments therebetween. 4. In an apparatus of the class described, circumferentially-spaced electrodes separated by intermediate die sections insulated therefrom to 6. In an apparatus of the class described, circumferentially-spaced electrode segments separated by intermediate die segments insulated therefrom to provide for a long heating current path through the article being formed, said electrode segments being connected to the separate phase leads of a multiphase alternating current source.

7. In an apparatus of the class described, a pair of electrode die members separated by an intermediate die member insulated therefrom and providing a complementary die surface contacting with the article being formed, and a transformer for supplying heating current to rhe article and having its secondary connected through leads to the respective electrodes, said transformer being disposed adjacent said intermediatemember and having its secondary leads following closely the contour of said member and insulated therefrom.

8. In an apparatus of the class described, a pair of electrode die members separated by an intermediate die member insulated therefrom and providing a complementary die surface contacting with the article being formed, and a transformer for supplying heating current to the article and having its secondary connected through leads to the respective electrodes, said intermediate member being of electrically-conductive non-magnetic material and being divided into a plurality of insulated parts transverse to the direction of current flow through the'article in contact therewith.

WILLIAM E. CRAWFORD. 

